I don't have a peer-reviewed study to validate my wild hypothesis, I'm just a simple businessman, but if you go to the Pricing tier of the page, you'll see Free, and then several paid tiers of service. Then, when you go to subscribe to the Free 5 hours tier, you are asked for a credit card, email, among other things. The idea is to remove friction for easily sliding prospects down the funnel until they ultimately agree to pay you money. That's not pro bono, or public good no-strings-attached work, that's modern sales 101.
Offering a free service without any kind of barrier would be ridiculous. It is not unknown that free services would ask you for a credit card. For example, website hosting, at a lot of places would ask you for a credit card, even on a free plan. This is to distinguish between bots, scammers and spammers and real human users.
